Artemia swarm dynamics and path tracking

Artemia larvae may show swarming organization under the presence of a light spot, while being insensitive to several other external stimuli. In this paper, the dynamics of the Artemia population in response to this kind of stimuli has been exploited to design a robot moving inside the water and able to lead the direction of the group. The robot therefore implements external leadership, by driving the Artemia population along a set of desired trajectories. Experimental results and simulations based on a model of Artemia motion confirmed the suitability of the approach.     

Synthesis and crystal structures of 4,4′-bipyridinium and 2,2′-bipyridinium pentachloro complexes containing the polynuclear anions [Bi2Cl10]4− and [Bi4Cl20]8−

The compounds 4,4-bipyridinium(2+) pentachloro-bismuthate(III) (1), [4,4-(C₁₀H₈N₂)BiCl₅] and 2,2-bipyridinium(2+) pentachloro-bismuthate(III) (2), [2,2-(C₁₀H₈N₂)Bi₂Cl₁₀] have been obtained by reacting bismuthate oxide and 4,4-bipyridine or 2,2-bipyridine in HCl acid medium. They have been characterized by single crystal X-ray analysis. (1) crystallizes in the triclinic space group with a = 9.776(2), b = 11.009(3),c = 8.346(1) Å, = 101.58(2), = 98.63(2), and = 112.86(2)°. (2) crystallizes in the monoclinic space group P2₁/c with a = 14.239(2), b = 14.226(2), c = 16.275(3) Å, and = 110.15(2)°. The crystal structure of (1) consists of 4,4-bipyridinium(2+) cations interacting through hydrogen bonding with [Bi₂Cl₁₀]^2– dimers giving rise to endless double chains, while that of (2) is formed by 2,2-bipyridinium(2+) cations and [Bi₄Cl₂₀]^8– tetramers extensively interacting through hydrogen bonding. The different polynuclearity of the anions seems related to the different directions along which each cation can form hydrogen bond interactions.     

6-alkyl- and 5,6-dialkyl-2-methoxy-4(3H)-pyrimidinones in the transformations of pyrimidines. Regiospecific 1-N-acylation of pyrimidines.

Transformation of 6- and 5,6-dialkyl-2-methoxy-4(3H)-pyrimidinones (1a and 1b) into 1-$\text{N}$-acylated-pyrimidine derivatives 3($\text{a}$-$\text{f}$) under Friedel-Craft like conditions is presented. In different acylation conditions 4-O-acylated-pyrimidines (5a and 5b) are also obtained. Compounds (3c) and (3f) can be directly converted into 1-$\text{N}$-acyl-protected-isouridine analogues (8a and 8b).     

Mononuclear heterocyclic rearrangements. Part 12. Rearrangement of 1,2,4-oxadiazoles into indazoles

The first example of a mononuclear heterocyclic rearrangement involving an XYZ = CCN side-chain sequence is reported. The 3-(o-aminophenyl)-, and 3-(o-methylaminophenyl)-5-methyl-1,2,4-oxadiazoles ( 3a,b ) gave a thermally induced rearrangement into 3-acylaminoindazoles ( 4a,b ). On the other hand, the 3-(o-acetylaminophenyl)-5-methyl-1,2,4-oxadiazole ( 3c ) produced a base induced rearrangement into 3-acetylaminoindazole ( 4a ).     

Catalysis of oxo transfer to prochiral sulfides by oxovanadium(v) compounds that model the active center of haloperoxidases

The catalytic properties of a new class of chiral vanadium compounds--[(S,S,S)-VO(OMe)L1] (5), [(S,S)-VO(OMe)L2] (6), [(S,S)-VO(OMe)L3] (7), and [(R,R,R)-VO(OMe)L4] (8), as well as the system VO(OiPr)(3)/(R,R,R)-H(2)L4 [H(2)L1=(S,S)-bis(2-hydroxypropyl)-(S)-1-phenylethylamine, 1; H(2)L2=(S,S)-bis(2-hydroxypropyl)benzylamine, 2; H(2)L3=(S,S)-bis(2-hydroxypropyl)isopropylamine), 3; (H(2)L4)=(R,R)-bis(2-phenylethanol)-(R)-1-phenylethylamine, 4]--in the asymmetric oxidation of prochiral sulfides by organic hydroperoxides have been investigated. Particular attention has been paid to the factors that guide the discrimination between the two prochiral faces of the sulfides (methyl p-tolyl sulfide and benzyl phenyl sulfide), to steric implications stemming from the oxidant (cumyl hydroperoxide and tert-butyl hydroperoxide), and to the specific complex used. As an example, (S)-methyl p-tolyl sulfoxide was obtained in a 31 % enantiomeric excess by use of cumyl hydroperoxide as oxidant and complex 5 as the catalyst, after 150 min at 0 degrees C and with 100 % conversion of the sulfide. The crystal and molecular structures of 5 and 6 reveal the close relationship between these complexes and the active center of vanadate-dependent haloperoxidases: the vanadium is in a slightly distorted trigonal-bipyramidal environment with the nitrogen and the methoxy group in the axial positions, and the oxo and alkoxide functions of L2 and L3 are the plane. The presence and equilibrium situation of isomers of the catalysts in solution has been investigated by (51)V EXSY and variable-temperature multinuclear NMR spectroscopy. An intermediately formed peroxo (ROO(-)) vanadium complex was detected by (51)V NMR spectroscopy.     

Beiträge zur Chemie der Pyrrolpigmente, 77. Mitt. Synthese und Struktur vonb-Nor-bilatrienen-abc undb-Nor-biladienen-ac bzw. Bi-9,9′-dipyrrinonylidenen und Bi-9,9′-dipyrrinonylenen

B-Nor-biladienes-ac are prepared by oxidative coupling of dipyrrinones in nearly quantitative yields. Further oxidation of these derivatives yieldsb-nor-bilatrienes-abc. Constitutions, tautomerism, configurations at exocyclic double bonds, and conformations at exocyclic chromophore single bonds are determined for the crystalline state and their states of solution using X-ray structural analysis and spectroscopic methods, respectively.B-nor-biladienes-ac are found to be of (4Z,15Z)5sp,9sc,14sp geometry,b-nor-bilatrienes-abc are planar systems of (4Z,9E,15Z) configuration in the crystal, whereas in solutions there are indications of a more twisted conformation at their exocyclic chromophore single bonds.

Herr Dipl.-Ing.Heinz Flödl hat uns am 11. April 1988 für immer verlassen — wir trauern um ihn.     

Perfusion and chemical monitoring of living cells on a microfluidic chip

A microfluidic device that incorporates continuous perfusion and an on-line electrophoresis immunoassay was developed, characterized, and applied to monitoring insulin secretion from single islets of Langerhans. In the device, a cell chamber was perfused with cell culture media or a balanced salt solution at 0.6 to 1.5 microL min(-1). The flow was driven by gas pressure applied off-chip. Perfusate was continuously sampled at 2 nL min(-1) by electroosmosis through a separate channel on the chip. The perfusate was mixed on-line with fluorescein isothiocyanate-labeled insulin (FITC-insulin) and monoclonal anti-insulin antibody and allowed to react for 60 s as the mixture traveled down a 4 cm long reaction channel. The cell chamber and reaction channel were maintained at 37 degrees C. The reaction mixture was injected onto a 1.5 cm separation channel as rapidly as every 6 s, and the free FITC-insulin and the FITC-insulin-antibody complex were separated under an electric field of 500 to 600 V cm(-1). The immunoassay had a detection limit of 0.8 nM and a relative standard deviation of 6% during 2 h of continuous operation with standard solutions. Individual islets were monitored for up to 1 h while perfusing with different concentrations of glucose. The immunoassay allowed quantitative monitoring of classical biphasic and oscillatory insulin secretion with 6 s sampling frequency following step changes in glucose from 3 to 11 mM. The 2.5 cm x 7.6 cm microfluidic system allowed for monitoring islets in a highly automated fashion. The technique should be amenable to studies involving other tissues or cells that release chemicals.     

Metal content in river suspended particulate matter: data on Po River

The present study summarizes the last ten years of literature on heavy metal distribution in Suspended Particulate Matter (SPM) and dissolved phase in the Po River (Italy). The work compares different methodologies employed to collect, concentrate and fractionate the samples. The importance of metal speciation as a function of particle size is underlined and two approaches to metal speciation in the colloidal fraction of Po River SPM are presented: Sedimentation Field-Flow Fractionation (SdFFF) and pH-dependent extractions. Finally, emphasis is placed on the need for comparison with a reference "natural background level" of the metal load in Po River particulate matter in order to determine the real human contribution to river pollution. The high values of some trace transition elements, such as Cr and Ni, have been compared with clay sediments around Ferrara and with bricks in historic buildings. The highly comparable natural concentration of these metals in Po fine sedimentary rocks and in historic brick buildings of Ferrara (XII-XVI centuries) can provide information on natural geochemical anomalies.     

Macromolecular conformations at the water-air interface: Interactions between alpha and beta conformations of polypeptides

Bidimensional miscibility between alpha and beta conformations of polypeptides was investigated at the water-air interface in the 15°–30°C temperature range. The polypeptides were poly--methyl-L-glutamate (PGMG), poly--benzyl-L-glutamate (PGBG) and poly--benzyl-L-aspartate (PBBA). The polypeptide conformations, alpha or beta, were checked by IR spectroscopy using the MIR technique.The spreading isotherms for mixed monolayers alpha-PGMG/alpha-PGBG and beta-PGMG/beta-PBBA showed bidimensional miscibility both for alpha-alpha and beta-beta mixtures.For the alpha-alpha system, attractive interactions among the polypeptide alphahelices were found (G_mix<0) and the driving factor appeared to be the entropic one (packing). Compressibility moduli and surface potential measurements showed a fluidification effect of alpha-PGBG on mixed monolayers. In the case of beta-beta mixed monolayers, ideal behaviour was observed and no fluidification effect detected.Scanning electron micrographs made on collapsed monolayers showed hexagonal structures for alpha-alpha mixtures and no well-defined or characterized features for the beta-beta system.     

Polypeptides mixed monolayers: collapse mechanism

The mechanism of the collapse process of monolayers of poly-L-alanine and of its mixtures with poly--methyl-L-glutamate was studied at the water/air interface at temperatures of 15°, 20°, 25°, and 30 °C.From measurements of the collapse surface pressure as a function of molar ratios and from the determination of the collapse kinetics, as well as from ellipsometrical measurements of the thickness of the film, the complete solubility of the components, even in the collapsed phase, was deduced.Furthermore, activation energies and values ofG*,H*, andS* in relationship to the kinetics of this process were deduced; it was shown that this process is constituted of a first phase of nucleation and of a second phase of growth both for the poly-L-alanine alone and for its mixtures with poly--methyl-L-glutamate.